PSI - Issue 79

Karolina Głowacka et al. / Procedia Structural Integrity 79 (2026) 155– 160 159 In the first approach to determine the fatigue characteristic, the relationship between the strain range ∆ and the number of cycles to failure ( ) was analyzed. The obtained results are shown in Figure 4a. As seen from the graph, the data points are randomly distributed, indicating that this approach does not provide a consistent fatigue relationship. A second approach, based on the maximum strain versus the number of cycles to failure, yielded a clear correlation, as presented in Figure 4b. Open squares correspond to samples tested without pre-strain, while filled squares represent those with approximately 10% pre-strain applied. The obtained data align along a nearly linear trend, and the resulting fatigue characteristic can be described by a reduced form of the Manson – Coffin – Basquin model [15 17], limited to its elastic component: = 0.426 ∙ (2 ) −0.206 . (1) This characteristic was determined in accordance with the ASTM standard [18]. It was observed that, regardless of the presence of pre-strain, the same fatigue relationship can be applied. The introduction of pre-strain only broadened the range of experimentally obtained data, improving the representativeness of the results. a) b)

Figure 4. Determination of fatigue characteristics based on: (a) strain range and (b) maximum strain versus number of cycles to failure

4. Summary and conclusion The conducted experiments demonstrated that the fatigue life of the investigated composite is reliably characterized by the relationship between maximum strain and the number of cycles to failure. This relationship proved to be universal and remained valid regardless of the application of pre-strain. The fatigue characteristics may be described by equation = 0.426 ∙ (2 ) −0.206 . The introduction of pre-strain led to increased variability in the mean strain values, which, in turn, enhanced the reliability and statistical robustness of the obtained results. The observed behavior is consistent with general trends reported for composite fatigue; however, it also reveals specific features associated with rubber – cord reinforcement systems. From a practical perspective, the findings provide a basis for durability predictions of reinforced rubber elements commonly used in engineering applications, such as belts, tires, and damping components.